The invention relates to a method for fault detection in the load path of a spindle actuator which is provided for actuating an aerodynamically active surface, in particular a high lift surface of an aircraft, according to the preamble of claim 1, as well as a device for fault detection in the load path of such a spindle actuator according to the preamble of claim 11.
Document WO 2007/024220 A1 discloses a failure-tolerant redundant actuator system that is tolerant of single point failures.
In high-lift systems of aircraft common today, the individual high-lift surfaces or flaps are actuated in a manner mechanically coupled to one another by a central shaft line driven by a central drive. Such a centrally driven high-lift system is used, for example, in the Airbus A340 aircraft. However, forward-looking developments are going towards high-lift systems in which the flaps are actuated by electrically triggered individual drives. Such individually driven flaps make it possible to achieve high flexibility with regard to the actuation of the flaps and allows functionalities of the high-lift system which were not possible with the hitherto centrally driven flaps. A flap system having such individual drives is described, for example, in DE 103 13 728 A1. In one of the exemplary embodiments described therein, two individual drives are provided for actuating a single high-lift flap, which drives are coupled to the flap at positions spaced apart from one another and are electronically synchronised with one another as well as with the individual drives of the other flaps.
In order that the flaps of a high-lift system can reliably absorb the high aerodynamic loads occurring during their deployment without any undesirable change in their position, brakes are provided at suitable positions in the high-lift system by which means the shaft lines or drives can be fixed in the respective position as required. In particular, in the event of a rupture or other type of failure of load-bearing components in the high-lift system, which is highly improbable but cannot be excluded, such brakes should prevent any uncontrolled sudden change in the position of one or more of the high-lift flaps with the consequence of flying states which can possibly no longer be controlled.
The present requirements for safety in air transport require that firstly all critical load paths of said type should be designed as redundant so that in the event of failure of a primary load path, its function is at least partially taken over by a secondary load path and thus avoids a state which can no longer be controlled and secondly, that measures are taken for the early detection of already existing faults or faults being notified in the critical components of the high-lift system. In particular, it is important to avoid so-called “hidden failures” and to detect corresponding faults as far as possible within a flight cycle.